This invention relates to a retaining wall structure constructed on a sloped cut earth portion, such as of a made land or a mountain surface, for preventing landslide. The present invention is also directed to a method of constructing the retaining wall structure.
In making a road on a mountain surface, the surface is first cut to form a sloped cut earth portion and a retaining wall is then constructed on the cut earth portion to prevent the landslide. The conventional retaining walls include a leaning type wall, a gravity type wall and a cantilever type wall.
FIG. 8 illustrates a typical conventional leaning type retaining wall structure Y.sub.1 in which a retaining wall 103 is constructed on a longitudinally extending cut earth portion 102 of a mountain surface 101 so as to lean against a sloped surface 122 of the cut earth portion 102. The retaining wall structure Y.sub.1 is constructed as follows. The mountain surface 101 is first cut to form the cut earth portion 102 having a longitudinally extending horizontal flat surface portion 121 and the sloped surface portion 122 obliquely upwardly extending from one side of the horizontal portion 121. The horizontal portion 121 has a transverse length (width) N.sub.1 which is greater than the width M of the road to be constructed. In order to minimize the amount of the cut earth while preventing the crumbling of the sloped earth wall 122, the inclination angle of the sloped wall is generally 5.degree.-10.degree. from vertical. Thus, in the formation of the cut earth portion 102, that part of the earth which is defined by the triangular cross-section A.sub.1 B.sub.1 C.sub.1 is removed. After the horizontal portion 121 and the sloped portion 122 have been formed, the retaining wall 103 is constructed along the sloped portion 122 such that the center of gravity G of the retaining wall 103 as constructed is located on an extension of the bottom line QP (which is in consistent with the horizontal line A.sub.1 B.sub.1 of the horizontal portion 121), i.e. a distance D from the corner P of the retaining wall 103. As a consequence, part of the weight of the retaining wall 103 is imposed on the sloped portion 122.
The structure Y.sub.1 shown in FIG. 8 has a problem that it is necessary to remove a large amount of the earth from the mountain surface 101 in order to provide a sufficient width N.sub.1 for forming the road. Thus, the earth cutting work requires great labor and long time. Further, since the thickness of the retaining wall is relatively small, the structure Y.sub.1 fails to exhibit a high landslide preventing strength.
FIG. 9 depicts a typical conventional gravity type retaining wall structure Y.sub.2 in which a heavy retaining wall 203 is constructed on a longitudinally extending cut earth portion 202 of a mountain surface 201. The retaining wall structure Y.sub.2 is constructed as follows. The mountain surface 201 is first cut to form the cut earth portion 202 having a longitudinally extending horizontal flat surface portion 221 and the sloped surface portion 222 obliquely upwardly extending from the horizontal portion 221. The horizontal portion 221 has a transverse length (width) N.sub.2 which is slightly smaller than the width M of the road to be constructed. Thus, in the formation of the cut earth portion 202, that part of the earth which is defined by the triangular cross-section A.sub.2 B.sub.2 C.sub.2 is removed. The length A.sub.2 B.sub.2 is equal to or greater than the width N.sub.2. After the horizontal portion 221 and the sloped portion 222 have been formed, the retaining wall 203 is constructed on the horizontal portion 221 and the space between the retaining wall 203 and the sloped portion 222 is filled with a suitable filler E such as earth and sand. The road is then constructed on the upper surface of the retaining wall and the fill.
The structure Y.sub.2 shown in FIG. 9 has a problem that it is necessary to remove a large amount of the earth from the mountain surface 201 in order to provide a sufficient width N.sub.2 for supporting the retaining wall 203 thereon. Since the retaining wall 203 prevents the landslide by its own weight, it is necessary that the width N.sub.2 of the bottom of the retaining wall 203 and, hence, the length A.sub.2hd B.sub.2 as well, should be sufficiently large. Thus, similar to the structure Y.sub.1, the earth cutting work requires great labor and long time.
FIG. 10 depicts a typical conventional cantilever type retaining wall structure Y.sub.3, in which an L-shaped retaining wall 303 composed of a horizontal section 325 and a vertical section 326, integrated with each other into a unitary structure, is constructed on a longitudinally extending cut earth portion 302 of a mountain surface 301. The retaining wall structure Y.sub.3 is constructed as follows. The mountain surface 301 is first cut to form the cut earth portion 302 having a longitudinally extending horizontal flat surface portion 321 and the sloped surface portion 322 obliquely upwardly extending from the horizontal portion 321. The horizontal portion 321 has a transverse length (width) N.sub.3 which is slightly smaller than the width M of the road to be constructed. Thus, in the formation of the cut earth portion 302, that part of the earth which is defined by the triangular cross-section A.sub.3 B.sub.3 C.sub.3 is removed. The length A.sub.3 B.sub.3 is equal to or greater than the width N.sub.3. After the horizontal portion 321 and the sloped portion 322 have been formed, the retaining wall 303 is constructed on the horizontal portion 321 and the space defined between the retaining wall 303 and the sloped portion 322 is filled with a suitable fill E such as earth and sand. The road is then constructed on the upper surface of the retaining wall and the fill.
FIG. 11 shows another conventional cantilever type retaining wall structure Y.sub.4 which is the same as the structure Y.sub.3 except that a T-shaped retaining wall 403 is substituted for the L shaped wall 303. Thus, the reference numerals and symbols 401-403, 422, 425, 426, N.sub.4, A.sub.4, B.sub.4 and C.sub.4 in FIG. 11 correspond to 301-303, 322, 325, 326, N.sub.3, A.sub.3, B.sub.3 and C.sub.3, respectively, in FIG. 10. Because of the presence of an extended portion 427 in the horizontal section of the wall 403, the structure Y.sub.4 shows an improved earth retaining property as compared with the structure Y.sub.3.
The structures Y.sub.3 and Y.sub.4 shown in FIGS. 10 and 11 have a problem that it is necessary to remove a large amount of the earth from the mountain surface in order to provide a sufficient width N.sub.3 or N.sub.4 for supporting the retaining wall 303 or 403 thereon. Thus, similar to the above-described known structures, the earth cutting work requires great labor and long time. Further, since the weight of the fill E is relatively small, the structures Y.sub.3 and Y.sub.4 fail to exhibit a high landslide preventing strength.